Unless I'm missing something, you need evidence to back up any appeal. If both parties have different stories then the one who made the appeal needs to provide proof that they didn't rule break, or the admins story will be taken as fact no matter what.
This is a tough situation to crack.
As Kyber said, Because KOS was called on both people (CeeZee and someone else) another person is allowed to kill either of the KOS persons.
HOWEVER, as Miia states,
in this case as a rule states that you cannot join a fight unless you have some proof as to which is the traitor and I'm not sure how you can see 2 people screaming to KOS the other as proof.
It can also be classed as joining gunfights as Yikes had no way of knowing who is the traitor, and it was technically still in the middle of the gunfight.
I hope whoever is handling this takes their time with it, cos this is a tough one.